Methodological standards for body composition assessment-an expert-endorsed guide for research and clinical applications: bioimpedance, dual-energy X-ray absorptiometry, computerized tomography, and ultrasound methods.

The assessment of body composition has long been a fundamental component of research and is gaining increasing adoption in clinical practice. This growing interest has drawn new professionals to the field and increased emphasis on its clinical relevance and applications. However, the diversity of assessment techniques and inconsistent terminology create challenges, highlighting the urgent need for harmonized approaches across research and healthcare settings. Commonly employed methods include bioelectrical impedance approaches, dual-energy X-ray absorptiometry, and computerized tomography, with ultrasound emerging as an increasingly prominent tool. These methods are featured in guidelines for diagnosing conditions such as low muscle mass, malnutrition, sarcopenia, and sarcopenic obesity, among others. This second narrative review in a series, developed by an international panel of experts, focuses on these widely accessible assessment tools that align with clinical recommendations. It presents foundational knowledge, discusses validity and reliability considerations, and offers practical advice on terminology, measurement protocols, data interpretation, and longitudinal monitoring. The report also addresses current limitations and identifies areas needing further research. Our goal is to provide clear, evidence-based guidance that is useful for both experienced practitioners and those newly engaging with body composition assessment. We urge organizations, journals, and stakeholders across the body composition field to adopt the proposed principles and standards to support consistency, transparency, and scientific rigor in both research and clinical care.